Currently, it is estimated that manufacturing associated waste generates over 50 million pounds of low density polyurethane foam each year. This form is generally disposed of in land-fill operations. Because of the economic loss associated with both the land required for land-fill and the foam disposed of in these operations, it is highly desirable to utilize the scrap foam or its chemical components in new product manufacture. One such chemical component which can be recovered from the scrap foam, and which is of particular commercial interest, is polyol, which can be used to manufacture new foam.
Prior art polyol recovery processes have included dissolving the foam and subsequently using the resulting solution without further purification to make new foam. In German Pat. No. 2,738,572, polyurethane wastes are heated in a diol containing a basic catalyst to prepare a homogenous polyol component to be used in the production of new foam. U.S. Pat. No. 2,937,151 to Broeck et al teaches dissolving scrap foam in high molecular weight polyesters, polyester amides or polyalkylene ether glycols, similar to those used to make the foam; the resulting solution is then crosslinked with isocyanate to generate new foam. Heiss, in U.S. Pat. No. 3,123,577, mills cellular polyurethane plastic, dissolves the particules in a high molecular weight trihydric polyalkylene ether containing a tin catalyst, and reacts the resulting resin with polyisocyanate to form new cellular polyether polyurethane. Tucker et al, in U.S. Pat. No. 3,983,087, heat scrap foam in a glycol wherein the alkylene chain separating the hydroxyl groups is branched. This homogeneous mixture can be used to make new foam. Braslaw et al, in U.S. Pat. No. 4,159,972, dissolve the foam in a low molecular weight diol, admix a high molecular weight polyol therewith, remove the diol under vacuum and use this product to make new foam. Kinoshita, in U.S. Pat. No. 3,632,530 heat the foam in a glycol and an amino compound in the presence of a tertiary amine catalyst. Upon standing, the mixture separates into a glycol containing amine layer and a layer comprising polyalkylene ether polyol. The polyol layer is used to produce new foam. Frulla et al., in U.S. Pat. No. 3,738,946 heat scrap foam in an aliphatic diol, preferably in the presence of a dialkanolamine. The resulting material is used without further purification to make new foam. U.S. Pat. No. 3,708,440 to Frulla et al is similar, employing an aliphatic diol and a dialkanolamine. McElroy, in U.S. Pat. No. 3,300,417, liquifies a polyurethane plastic by heating the polyurethane in an organic liquid in the presence of a metal catalyst, preferably a tin compound. The resulting liquid is reacted with a polyisocyanate to prepare a new cellular polyether polyurethane.
Hydrolysis has also been used on polyurethane foam to recover polyol. Lohr, in U.S. Pat. No. 4,035,314, hydrolyzes foam using superheated steam, dissolves the resulting oily residue in solvent, and further treats this mixture by a process comprising gassing with hydrochloric acid gas and ultimately recovering polyol. Pizzini et al, in U.S. Pat. No. 3,441,616, hydrolyze a polyether polyurethane foam with a strong base in a dimethylsulfoxide-water medium, extract the resulting polyol with a hydrocarbon solvent immiscible with the hydrolysis medium, separate the polyol solvent layer and strip off the solvent to recover polyol.
In spite of the numerous known processes for scrap foam utilization and polyol recovery, however, scrap foam is still generally disposed of in land-fill operations, indicating that none of these polyol recovery processes is commerically feasible. Therefore, a commercially feasible process for high grade polyol recovery has continued to be the subject of research.
An object of the subject invention is the recovery from scrap or waste polyether polyurethane foam of substantially pure polyether polyols, which, unlike prior art recovered polyol, are physically and chemically indistinguishable from the virgin polyol used to make the original foam, and may then be used to produce a high quality flexible foam of high resilience.
A further object of the invention is the processing of the foam in a commercially economical and rapid manner.